This study is designed to evaluate the safety of vigabatrin as monotherapy in adult patients with complex partial epilepsy. In addition, continued efficacy of vigabatrin as a monotherapy will be evaluated. Vigabatrin causes suppression of seizure incidence in complex partial seizure models (kindling, pilocarpine) and generalized tonic-clonic seizure models (audiogenic, photic, seizure-prone gerbil, hyperbaric oxygen, maximal electroshock, and chemically-induced models). Vigabatrin had both proconvulsant and anticonvulsant efects in a generalized absence model (seizure-prone rats). Seizure symptoms were exacerbated after electrical stimulation of the spinal cord. These results suggest that vigabatrin is particularly effective in generalized convulsive seizure models and partial complex models. The anticonvulsant effect of vigabatrin is potentiated by the inhibitory neurotransmitter glycine. Clinical trials have shown that the addition of vigabatrin to standard antiepilepsy therapy significantly decreases seizure frequency and severity in patients with focal epilepsy whose seizures have been difficult to control. Efficacy results in 'add-on' trials, coupled with a favorable safety profile suggest vigabatrin be studies as a monotherapy.